It begins this way:"Love isn’t the only thing money can’t buy—blood is, too. And yet, though no money is exchanged, blood can find ways of getting to the people who need it, though not often in ways where demand and supply are aligned. In the days following the Boston Marathon bombing, people rushed to give blood in support of the victims, eager to donate one of the human body’s most precious resources to others, free of charge.

"While this altruistic impulse is certainly commendable, according to Carmen Wang, it is sometimes misguided. “In that instance, the American Red Cross had to issue an announcement thanking would-be donors and informing them that they already had an adequate supply of blood.” But at other times, for example when the flu or cold virus afflicts many regular donors, blood supply dips, and blood banks have trouble finding people willing to give."